I've been wanting to "follow" Sing from Mousesports even while he isn't streaming for quite some time. I tried adding him but "no go". A feature like this would solve the issue and widen up the "improving skill" chances for everyone.

That's pretty damn cool being able to follow pro games in their pub matches even if there was no commentary it would be pretty useful. Pro player gets money, Valve gets money, we get knowledge I like this feature.

Since I proposed a somehow similar idea to this one a few months ago, I wholeheartly agree to this one. Always fun to watch Dendi play on pubs
(as one of comments from that thread - 'It's a stalker's dream')

I like the part with paying to the players, but then again it would totally ruin streaming sites, and I don't think that Valve wants to do that. Then again, there are some variations of this idea that will be useful and harmful for every side.

Excellent idea, I fully support this.
In response to the previously posted statement that this will hurt streaming sites, consider that the Defense ingame also hurts streaming sites, but there are still huge numbers of people watching online rather than ingame because (a) you don't need dota 2 installed and (b) it's free.